Mining, construction, forestry, agriculture, landscaping, and material handling industries use a variety of heavy equipment for moving earth and other materials. Hydraulic and electric excavators, backhoes, shovels, and drills are examples of equipment commonly used at, for example, mining or construction sites. The pieces of equipment are heavy-duty equipment, which are mobile and some are capable of moving thousands of kilograms of material at a time. The drive system underneath heavy equipment may include axles with wheels or a track-type undercarriage. A track undercarriage is used to move the heavy equipment and large amounts of material over many types of terrain. Track undercarriages are intended to operate on a variety of terrain conditions and can handle a higher operating weight capacity than comparably sized wheeled assemblies.
Track undercarriages include a track located on each side of a piece of heavy equipment underneath the equipment in a similar location to where wheels are located on wheeled equipment. A track undercarriage is used in place of wheels and operates with a drive mechanism to rotate the track to propel the heavy equipment. Each track on either side of the equipment rotates around an oblong undercarriage frame. The track is made up of a series of individual track shoes linked together in a continuous chain. The track undercarriage includes a series of rollers which allow the track to rotate about the undercarriage frame. Rollers include lower rollers or track rollers, upper rollers or carrier rollers, and idler rollers.
The track rotates around an undercarriage frame and is driven by a sprocket. The sprocket is located on one end of the track, typically the rear, and an idler roller supports the opposite end of the track, typically the front. In between the idler and sprocket, a plurality of rollers supports the undercarriage frame and rotates as the track rotates around the undercarriage frame. Rollers provide a low friction surface for the track to move along as the heavy equipment moves along the terrain. Rollers can be located above and below the undercarriage frame on the track. A track moves over the sprocket, over the upper rollers, around the idler at the front of the undercarriage, then under the lower rollers where the track also contacts the ground. An undercarriage typically includes at least one upper roller and several lower rollers. A large shovel, for example, may have two upper rollers, and idler roller, and seven or eight lower rollers. The rollers are load bearing, with some rollers being stressed by the weight of the heavy equipment more than other rollers. The rollers are metal and are typically made of steel and include metal bushings or bearings, typically made of bronze, to reduce friction between parts of the roller assembly.
The roller bushings are located inside the roller assembly and are lubricated in order to allow rollers to rotate with less friction. Roller assemblies may be designed with the bushing fixed, for example, within an end cap in which the roller rotates within the bushing. In an alternative design, the bushing is fixed within the roller body and both the bushing and roller body rotate around a shaft. Ideally, roller assemblies and bushings are well-lubricated and to maintain a low-friction contact surface between the bushing and the roller or between the bushing and shaft. Inadequate lubrication of the contact surfaces increases friction between the bushing and roller assembly which wears down the bushing eventually causing damage to the roller assembly. Even with adequate lubrication, bushings are subject to stress from contact with the roller or shaft and wear out over time. Because bushings and lubricant are internal to a roller assembly, the wear status of the bushings and amount of lubricant within the roller assembly are difficult to monitor.
Roller assemblies within a track undercarriage typically fail due to lack of adequate lubrication. Without adequate lubrication, friction between the rollers and bushings or bushing and shaft increases substantially and causes wear to the components. One indicator of inadequate lubrication is increased heat within the roller assembly. A current approach to monitoring rollers requires a person to measure the temperature of the rollers by walking next to the equipment as the equipment is driven and take periodic temperature readings of the rollers using a laser-sighted infrared gun-style thermometer. The current approach is dangerous for the person taking temperature measurements, because the measurement device requires the person to remain in close proximity to the heavy equipment while the equipment is operating. Further, manual monitoring of roller temperature requires expensive labor, and roller temperature is simply not monitored during everyday operation of the heavy equipment. Another approach to managing a track undercarriage is to inspect and repair components during a pre-scheduled preventative maintenance of the equipment. Often, lubricant and bushings wear out or problems occur before the periodic maintenance.
Without constant monitoring of the roller assemblies on a track undercarriage, lubricant problems go unnoticed and bushings tend to wear down completely before the wear is noticed leaving rollers without any bushings. If a bushing wears down completely and a roller continues to run without a bushing, damage occurs to the roller as the roller contacts other surfaces within the roller assembly. The metal on metal or steel on steel contact between the roller and other roller assembly components results in the surface of the roller and other components to wear and deteriorate beyond the point at which the parts can be repaired. Eventually, a roller without lubricant or a bushing will wear down and stop turning altogether. A track undercarriage is likely to break down at the point of use when a roller stops turning unexpectedly. Equipment that breaks down at a work site creates additional hazards and maintenance problems in addition to adding cost to repairs and replacements. However, if lubricant problems or bushing wear is caught early, a roller assembly can be repaired. Repair of roller assembly components is less expensive than replacement with a new roller assembly.